Many types of rangefinders are known, for example, one type of rangefinder generally comprises an infrared light emitting diode (LED) and a photodiode. The rangefinder emits an infrared pulse, which is reflected by a nearby object. The rangefinder receives the reflected infrared signal. Characteristics of the reflected infrared signal such as intensity, time of flight, frequency and/or phase are then analyzed to derive the object's range.
Another type of known rangefinder is the common radar system. An emitter, for example, a narrow beam width antenna such as a parabolic antenna, emits a radio frequency pulse (sometimes denoted as a signal beam). Radio reflective materials of objects within the signal beam reflect the signal back to the emitter. Measurements of the reflected signal's time of flight and Doppler shift are then used to compute the object's range, and in some systems, velocity.
Range-finding systems and methods, i.e., systems and methods for determining the distance between two objects, are often related to object positioning systems and methods. For example, object positioning systems usually use range-finding methods to first determine the distance between a target object and each of one or more reference objects, and then determining the position of the target object. Examples of known object positioning systems include the Global Positioning System (GPS) of the United States, the Global Navigation Satellite System (GLONASS) of Russia, the Galileo positioning system of the European Union, and the BeiDou Navigation Satellite System of China.
A difficulty with these systems is that the propagation speed of the emitted radio frequency (RF) signal, which is substantially the speed of light, is so high that even small errors in time of flight measurement amount to large errors in distance calculation, which results in more stringent and costly system requirements, e.g., precise time synchronization, wide signal bandwidth, and the like.